This is an application for a multi-disciplinary Center for Sexually Transmitted Diseases at the University of North Carolina at Chapel Hill. Investigators from the School of Public Health, the School of Medicine, and the Academic Affairs (liberal arts) campuses of UNC-CH combine their talents in an interactive set of projects that will help to design better strategies to prevent sexually transmitted infections. There are six projects and three supporting core units. Project 1 (P.F. Sparling, PI) examines the structure and function of Neisseria gonorrhoeae iron regulated outer membrane proteins. Project 2 (J. Cannon, PI) examines the molecular biology and pathogenic properties of Neisseria gonorrhoeae Opa outer membrane proteins. Project 3 (M.S. Cohen,PI) establishes a human volunteer facility in the clinical research center of UNC Hospitals in which defined mutants lacking putative virulence factors of Neisseria gonorrhoeae are inoculated under controlled conditions into the urethra of male volunteers. The question is whether loss of particular surface proteins critically alters ability to cause infection. Project 4 (L.V. Stamm, PI) examines the structure and roles in pathogenesis and immunity of certain T. pallidum proteins. Project 5 (P. Wyrick, PI) investigates the expression of Chlamydia trachomatis proteins on the surface of epithelial cells in vitro. Each of these five basic science projects has components of microbiology, molecular biology, and genetics, and most have important components of immunology. Each is relevant to vaccine development against the respective organisms. Project 6 (J. Thomas, PI) will examine the behavior and epidemiology of core high frequency STD transmitters in Wilson County, North Carolina, a rural environment in which STDs are a major and poorly understood problem. These studies will pave the way for future interventional efforts designed to decrease the incidence of STDs. These projects will be supported by three cores: an Administrative Core; a Microbiology Core which will relate the arenas of behavioral and epidemiological studies to the basic science projects; and, a Developmental Project Core which will provide small starter grants for new investigators with novel ideas for STD related basic science or behavioral and epidemiological studies.